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发表于 15-2-2012 21:36:28
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现代悬架开发的流程
The process entails
selecting appropriate vehicle level targets 选择合适的整车级目标
selecting a system architecture 选择系统级架构
choosing the location of the 'hard points', or theoretical centres of each ball joint or bushing 选择硬点
selecting the rates of the bushings 设计衬套的刚度
analysing the loads in the suspension 分析悬架的动静载
designing the spring rates 计算弹簧等刚度
designing shock absorber characteristics 设定减振器的特性曲线
designing the structure of each component so that it is strong, stiff, light, and cheap 进行悬架零件的详细设计,以保证零件的刚度强度,耐久,重量,物料成本
analysing the vehicle dynamics of the resulting design 进行整车的动力学计算
这整个过程有的是循环的,而且每一步都会涉及到很多专业细节,要小心对待。以下一个一个详细的说明,一下说明并没有考虑所有应考虑的因素,但是包含最重要的一些因素。
Vehicle level targets 整车级目标
Vehicle level targets 整车级目标,
A partial list [1] would include:
maximum steady state lateral acceleration (in understeer mode) 若是不足转向车辆,最大稳态侧向加速度
roll stiffness (degrees per g of lateral acceleration) 侧倾刚度(deg/g)
ride frequencies 偏频
lateral load transfer percentage distribution front to rear 前后桥的侧向力转移比,这个和前后桥的质量比要对应
Roll moment distribution front to rear 侧倾力矩前后分配
ride heights at various states of load 不同载荷情况下的ride height,
Understeer gradient 不足转向梯度,这个不懂的话,可以参考汽车理论看看,它的单位是deg/g,
Turning circle 最小转弯直径,这个要看竞争对手都是什么值
Ackermann 阿克曼,
Jounce travel 上跳行程
Rebound travel 下跳行程,这两个对舒适性很重要
Once the overall vehicle targets have been identified they can be used to set targets for the two suspensions. For instance, the overall understeer target can be broken down into contributions from each end using a Bundorf analysis
此外还有车身侧倾角、横摆角速度、质心侧偏角等反映整车操
纵稳定性的参数
System architecture 系统架构
System architecture
Typically a vehicle designer is operating within a set of constraints. The suspension architecture selected for each end of the vehicle will have to obey those constraints. For both ends of the car this would include the type of spring, location of the spring, and location of the shock absorbers. 实际进行底盘设计的时候,会受到很多约束,所以悬架架构选择应在这些约束以内,架构选择包括弹簧类型,位置,减振器位置,悬架形式,对于前后桥来说都是这样。
For the front suspension the following need to be considered 对于前悬来说,要考虑:
the type of suspension (MacPherson strut or double wishbone suspension) 悬架类型(麦弗逊,双横臂还是?)
type of steering actuator (rack and pinion or recirculating ball) 转向机(齿轮齿条还是循环球)
location of the steering actuator in front of, or behind, the wheel centre 转向机位置
For the rear suspension there are many more possible suspension types, in practice.
后悬,类似
Hardpoints 硬点
Hardpoints 硬点
The hardpoints control the static settings and the kinematics of the suspension. 硬点决定了悬架的几何运动特性和静态参数
The static settings are
Toe 前束
Camber 外倾
Castor 后倾
Roll center height at design load 设计状态的侧倾中心
Mechanical (or caster) trail 后倾拖距
Anti-dive and anti-squat 抗制动点头和驱动后座
Kingpin Inclination 主销内倾
Scrub radius 磨胎半径
Spring and shock absorber motion ratios 弹簧和减振器的运动比
The kinematics describe how important characteristics change as the suspension moves, typically in roll or steer. They include 以下是悬架运动学分析的,是车轮在上下跳以及转向时怎么运动的一些描述,他们对操稳和舒适性都很重要。
Bump Steer
Roll Steer
Tractive Force Steer
Brake Force Steer
Camber gain in roll
Castor gain in roll
Roll centre height gain
Ackerman change with steering angle
Track gain in roll
The analysis for these parameters can be done graphically, or by CAD, or by the use of kinematics software. 这部分可以在三维cad软件里做,当然也可以用多体软件,如adams来做。
Compliance analysis 柔性分析(弹性运动学分析)
Compliance analysis柔性分析(弹性运动学分析)
The compliance of the bushings, the body, and other parts modify the behaviour of the suspension. In general it is difficult improve the kinematics of a suspension using the bushings, but one example where it does work is the toe control bush used in Twist-beam rear suspensions. More generally, modern cars suspensions include an NVH bush. This is designed as the main path for the vibrations and forces that cause road noise and impact noise, and is supposed to be tunable without affecting the kinematics too much;
由于悬架中存在很多弹性件,包括衬套,稳定杆,甚至金属的零件,都存在一些弹性,所以在受到载荷的时候,会发生一定的变形,我们在进行悬架设计的时候要对这些变形进行控制,让他们以我们想要的方式变形,这部分可以用多体软件来进行计算,如adams,或者其他一些悬架分析软件如,suspensionsim等
要设计衬套的刚度,必须进行这部分的分析。
Loads 载荷分析
Loads
Once the basic geometry is established the loads in each suspension part can be estimated. This can be as simple as deciding what a likely maximum load case is at the contact patch, and then drawing a Free body diagram of each part to work out the forces, or as complex as simulating the behaviour of the suspension over a rough road, and calculating the loads caused. Often loads that have been measured on a similar suspension are used instead - this is the most reliable method.
我们知道,汽车运行的各种工况下,悬架零件都会受到各种各样的力,我们要保证悬架零件在生命周期不会失效,就需要进行载荷分析,将汽车常见的工况进行归纳总结,然后在轮心施加相应的载荷,然后计算个零件的受力,之后提交给有限元进行强度,刚度,疲劳等计算和优化,这反过来也会促进前面的硬点进行微调,以使各零件载荷比较合理。
Detailed design of arms 零件的详细设计
Detailed design of arms 零件的详细设计
The loads and geometry are then used to design the arms and spindle. Inevitably some problems will be found in the course of this that force compromises to be made with the basic geometry of the suspension.
这部分设计要使零件能够承受上面所计算的载荷,同时不能有零件干涉,零件的重量和物料加工成本也会详细考虑,这部分有时也会推动前面的设计进行优化
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